Device for measuring the solidification temperature of liquids

ABSTRACT

To measure the solidification temperature of liquids a device is used comprising a heatable and coolable receptacle for a sample of the liquid, a temperature sensitive element and in the receptacle in the vicinity of the temperature sensitive element means to produce a local supercooling.

United States Patent Hummel et al.

DEVICE FOR MEASURING THE SOLIDIFICATION TEMPERATURE OF LIQUIDSInventors: Heinz Hummel; Herbert Gortz, both of Frankfurt/Main, GermanyFarbwerke Hoechst Alrtiengesellschaft vormals Meister Indus and Bruning,Frankfurt/Main, Germany Filed: Nov. 20, 1970 Appl. No.: 91,451

Assignee:

Foreign Application Priority Data Nov. 21, 1969 Germany ..P 19 58 476.0

US. Cl. ..73/17 R Int. Cl. ..G0ln 25/04 Field of Search ..73/ 17 1 Oct.3, 1972 [56] References Cited UNITED STATES PATENTS 3,457,771 7/1969Davis ..73/17 2,635,455 4/1953 Staehling .L..' ..73/17 3,060,318 10/1962ouvlald ..73/17 X Primary Examiner-James J. Gill 7 AssistantExaminer-Herbert Goldstein Attorney-Connolly and Hutz [57] ABSTRACT Tomeasure the solidification temperature of liquids a device is usedcomprising a heatable and coolable receptacle for a sample of theliquid, a temperature sensitive element and in the receptacle in thevicinity of the temperature sensitive element means to produce a localsupercooling.

6 Claims, 1 Drawing Figure PATENTEDnm 3 m2 INVENTORS HEINZ HUM MELHERBERT GORTZ Y clmwazm 1% AT TORNEYS DEVICE FOR MEASURING THESOLIDIFICATION TEMPERATURE OF LIQUIDS The present invention relates to adevice for measuring the solidification temperature of liquids.

Devices for determining the solidification temperature have beenproposed, comprising a heatable and coolable receptacle for the sampleand in the interior thereof a thermometer and optionally a stirringdevice. The known devices have the drawback that the measuring result isfalsified always by supercooling of the sample at a temperature belowthe solidification temperature. By additional manual rubbing of thethermometer on the wall of the receptacle and adding seed crystals themeasuring error may be somewhat diminished depending on the skill of themeasurer.

It has now been found that the aforesaid drawbacks can be avoided when,for measuring the solidification temperature of liquids, a device isused comprising a receptacle for a sample of the liquid, means forheating and cooling, and a temperature sensitive element, in whichdevice in the receptacle for the sample near the temperature sensitiveelement means are provided for to produce a local supercooling. Themeans to produce a local supercooling are suitably arranged between thebottom of the receptacle and the temperature sensitive element. As meansto produce a local supercooling there may be used at least one gasoutlet or a thermoelectric cooling element.

It is expedient to dimension the gas outlet in a manner such that thegas bubbles are as small as possible, preferably have a diameter of from0.1 to-O.8 millimeter and get into the sample in the direct vicinity ofthetemperature sensitive element so that a strong local supercooling canbe produced.

The device according to the invention is suitable for the constructionof automatic instruments to determine the solidification temperature inproduction control. It can also be used, however, to carry out reliableand rapid routine analyses in laboratories.

The device according to the invention is now illustrated with referenceto the accompanying drawing. The receptacle for the sample 1 suitablyhas a double wall and is provided with an inlet and outlet 2 and 3 forthe sample, an inlet each for the cooling and heating medium 4 and 5,and an outlet 6 therefor. It is also possible, of course, to use,instead of the double-walled receptacle, receptacles with known heatexchange means, such as cooling coils and the like. In the interior ofthe receptacle for the sample a temperature sensitive element 7 isarranged and between the said. temperature sensitive element 7 and thebottom of the receptacle at least one gas outlet 8 or a thermoelectriccooling element is fixed, preferably on the extended axis of thetemperature sensitive element. In the drawing there is shown manuallyoperable value but not the valves required for automatic operation inthe inlets and outlets for the sample, the heating and cooling mediumand the supply pipe for the gas outlet 8, nor the control mechanisms forthe valves, and the electronic control and regulating elements for themeasuring and control mechanisms.

After introducing the sample into the device of the invention, inlet 2into receptacle 1 is closed and the receptacle is heated, for example bymeans of steam supplied through inlet 5. In general, it is sufficient toheat the sample 10 to C above the respective solidification temperature.When the desired value is reached, the supply of steam is discontinued,which, in the case of an automatic operation, may be done by athermocouple. After switching off the heating, the sample is cooled, forexample by introducing cooling air into the heat exchange jacket of thereceptacle, and simultaneously gas is introduced in the form of smallbubbles into the sample in the direct vicinity of the temperaturesensitive element 7. The introduction of air may likewise be controlledautomatically. When approaching the solidification temperature, i.e.,when the cooling rate of the sample diminishes owing to a beginningcrystallization, the current of gas bubbles is interrupted, in the caseof an automatic operation by means of a suitable control mechanism, forexample a differential amplifier which is actuated when the cooling ratefalls below a given value. From that time on the temperature of thesample approaches a constant value corresponding to the solidificationtemperature.

The above process can be practized as often as desired with and withoutchange of the sample. In connection with appropriate recording devicesand control mechanisms, the device of the invention can be operateddiscontinuously and automatically.

What is claimed is:

l. A device for measuring the solidification temperature of a liquidcomprising a receptacle for a sample of the liquid, heating and coolingmeans operatively associated with the receptacle for heating the liquidsample above its solidification temperature and cooling the liquid belowthe solidification temperature, a temperature sensitive element disposedwithin the receptacle for determining the temperature of the liquidsample particularly upon its solidification and for providing anindication of said temperature, a concentrated supercooling meansdisposed in said receptacle in the immediate vicinity of the temperaturesensitive element for producing a concentrated local supercooling in theliquid sample in the immediate vicinity of the temperature sensitiveelement, and said temperature sensitive element providing means fordetermining when the rate of cooling of the liquid sample in thereceptacle diminishes below a predetermined rate whereby the temperatureof the liquid sample in the receptacle approaches a substantiallyconstant value corresponding to its solidification temperature and thetemperature sensitive element is thereby caused to indicate thesolidification temperature of the liquid sample.

2. The device of claim 1, wherein the means to produce a localsupercooling in the receptacle for the sample are arranged between thebottom of the receptacle and the temperature sensitive element.

3. The device of claim 1, wherein the means to produce a localsupercooling consist of at least one gas outlet.

4. The device of claim 1, wherein the means to produce a localsupercooling consist of a thermoelectric cooling element.

5. A device as set forth in claim 1 wherein a recording device isconnected to the temperature sensitive element for providing a record ofthe temperature of the liquid sample as it approaches and arrives at itssolidification temperature.

6. A device as set forth in claim 1 wherein said concentratedsupercooling means includes means for terminating its operation.

it 1 f

1. A device for measuring the solidification temperature of a liquidcomprising a receptacle for a sample of the liquid, heating and coolingmeans operatively associated with the receptacle for heating the liquidsample above its solidification temperature and cooling the liquid belowthe solidification temperature, a temperature sensitive element disposedwithin the receptacle for determining the temperature of the liquidsample particularly upon its solidification and for providing anindication of said temperature, a concentrated supercooling meansdisposed in said receptacle in the immediate vicinity of the temperaturesensitive element for producing a concentrated local supercooling in theliquid sample in the immediate vicinity of the temperature sensitiveelement, and said temperature sensitive element providing means fordetermining when the rate of cooling of the liquid sample in thereceptacle diminishes below a predetermined rate whereby the temperatureof the liquid sample in the receptacle approaches a substantiallyconstant value corresponding to its solidification temperature and thetemperature sensitive element is thereby caused to indicate thesolidification temperature of the liquid sample.
 2. The device of claim1, wherein the means to produce a local supercooling in the receptaclefor the sample are arranged between the bottom of the receptacle and thetemperature sensitive element.
 3. The device of claim 1, wherein themeans to produce a local supercooling consist of at least one gasoutlet.
 4. The device of claim 1, wherein the means to produce a localsupercooling consist of a thermoelectric cooling element.
 5. A device asset forth in claim 1 wherein a recording device is connected to thetemperature sensitive element for providing a record of the temperatureof the liquid sample as it approaches and arrives at its solidificationtemperature.
 6. A device as set forth in claim 1 wherein saidconcentrated supercooling means includes means for terminating itsoperation.